1. Field of the Disclosure
The present disclosure relates generally to scanners, and more specifically, to an illumination assembly for a scanner.
2. Description of the Related Art
High speed scanners typically require high intensity illumination. One example of a light source that provides the required illumination is an external electrode xenon fluorescent lamp. However, various problems are associated with the use of a xenon fluorescent lamp as a light source. For example, a high power xenon fluorescent lamp must be used to generate the required illumination. Such high power lamps may generate excessive heat. To address this issue, a cooling fan and a vent may be positioned on the scanner; however, this adds cost and acoustic noise and, in some cases, may result in potential contamination through the vent. Further, the high power xenon fluorescent lamp needs a high frequency and high voltage inverter, which further adversely impacts the scanner both in terms of safety and signal quality.
Recent technological developments in the field of scanners have provided another light source, white LEDs (light emitting diodes). In many cases, one high power LED may be used in conjunction with a light guide to generate the required illumination. Alternatively, an array of medium power LEDs may be used. The array of medium power LEDs generates more light and is desired for high speed scanners. However, it is desired to use as few LEDs as possible to reduce the cost of the device. The white LEDs may be generally blue LEDs that use a blue LED die with yellow phosphor to form white light. Light produced by such LEDs may not be sufficiently mixed and direct incidences of such light at a target area, such as a sheet to be scanned, is not desired. Accordingly, it will be appreciated that an illumination assembly for a scanner that provides high intensity illumination in an efficient manner is desired.